Furthermore, the HER2 gene is located on chromosome 17q21-22, close to TOP2A, resulting in 33–60% of HER2-positive tumours containing concurrent modifications of TOP2A (Smith et al, 1993; Jarvinen et al, 2000; Bofin et al, 2003; Olsen et al, 2004). This evidence concerns the gene TOP2A and neoplasm.